This invention relates to a sliding member prepared by molding a resin composition.
A resin type sliding member, for example, a plain bearing, in which a lubricating oil is not used, is obtained by molding a resin composition in which an abrasion resistant synthetic resin is compounded with a lubricant and a reinforcing material. Various inventions have been made for enhancing the sliding characteristics at high temperatures of such sliding members.
For example, JP-B 4-65,866 (Prior Art 1) discloses a molded article of a resin composition composed of 100 parts by weight of a polyphenylene sulfide, 3 to 60 parts by weight of a fluoroplastic and 3 to 60 parts by weight of an aromatic polyamide fiber. Sliding members obtained from the above resin composition are stated to have excellent sliding characteristics.
JP-A 1-242,662 (Prior Art 2) discloses a resin composition composed of 10 to 90% by weight of an aromatic polyetherketone having added thereto 5 to 60% by weight of a carbon fiber and 5 to 30% by weight of carbon powder having an average particle size of 1-200 .mu.m. This resin composition is stated to be suitable as a material for a sliding member resistant to a high temperature and a high load.
JP-A 62-10,166 (Prior Art 3) discloses a sliding composition composed of 40 to 75% by volume of a heat resistant synthetic resin such as polyphenylene sulfide or the like, 5 to 25% by volume of an aromatic polyamide fiber, 5 to 30% by volume of a polytetrafluoroethylene (referred to hereinafter as PTFE) and 5 to 35% by volume of a lead oxide in which the volume ratio of PTFE to lead oxide is 1:0.5 to 1:1.5 and the total of the two is 15 to 55% by volume. A sliding member obtained from this resin composition is stated to have stable abrasion resistance in a high temperature zone without damaging a counter member even if the counter member is of a soft metal such as aluminum alloy or the like.
For example, a resin composition to be used in a bearing for a roller such as a heat roller or a press roller which forms a pair with the heat roller in a duplicating machine is required to have excellent sliding characteristics such as low frictional properties, abrasion resistance and the like over a range of from room temperature to a high temperature zone because the bearing is used over a range of from room temperature to a high temperature zone of about 150.degree. C.. In addition, in the case of a shaft composed of a soft metal such as aluminum alloy, stainless steel or the like, it is also important that the bearing therefor does not damage the shaft.
However, in Prior Art 1, the amount of a transfer film produced on the counter member is small, and hence, not only are the sliding characteristics insufficient, but also is the counter member damaged when the counter member is a soft metal shaft.
Also, in Prior Art 2, a carbon fiber is contained as a filler in a proportion of 5 to 60% by weight in a resin composition for a sliding member, and hence, there is also such a technical problem that the sliding member damages the counter member.
In Prior Art 3, the sliding member is provided with good sliding characteristics in a high temperature zone; however, there is such a technical problem that the abrasion resistance at ordinary temperature is not sufficient.